Remarks on Nika edulis, Risso

Miscellaneous .

493

in a very elegant manner in the form of a double comb, possess very
strong outlines in a great part of the retina. The retina of the
Plagiostoma also, both Sharks and Rays, contains fibres of a breadth
of as much as 0*01 mill., which exhibit all the characters of the
varicose fibres with double outlines which occur in the nervous centres.
Lastly, I have observed that in the eyes of many Dogs, the optic
nerve is still white at its entrance into the eye, and that it is only in
the retina that the nervous fibres become pale and transparent. But
the change takes place very soon after the entrance of the optic nerve,
whilst in the fishes just mentioned, the fibres with double outlines
extend over a great part of the retina, and only pass by degrees
to the aspect of the pale fibres. In a physiological point of
view it is remarkable that in the Fishes of which I am speaking,
notwithstanding the double outlines of the nervous fibres, the retina
appears to be tolerably transparent during life, whilst in the Rabbits
and Dogs it is opaque and white, in the whole extent of the fibres
with double outlines. In the former case the influence upon the
sight does not appear to be important, but in the latter the perception
of light must be hindered or disturbed as far as this peculiarity of
the fibres extends ; and the ophthalmoscopic effect of the bottom of
the eye, and especially of the entrance of the optic nerve, must present
remarkable modifications in all the animals in which a state similar
to that which has long been known in the Rabbit exists .—Comptes
Rendus , Oct. 20, 1856, p. 743.

Remarks on Nika edulis, Risso. By William Thompson.

The possession of a healthy specimen of Nika edulis has enabled
me to offer the following remarks, which, I trust, may add some¬
thing new to what is already known of this species.

The first specimen I obtained by dredging on the 2nd July, 1853.
I find by my notes, which were made at the time, that it was a
female, and in spawn ; the ova were darkish green, the animal itself
was of a cream colour, and spotted with red dots; the spots were
of different sizes, perfectly round, and rather thickly and regularly
placed. This specimen was dead before I examined it, and this will
account for the difference of colour as contrasted with the specimen,
the more immediate subject of the present paper. I had previously
obtained one specimen, and a third specimen, also in spawn, was
brought to me on the 20th July, 1855 ; the ova were bright green,
and the animal of a cream colour. This specimen was dead when
examined.

The subject of the present paper was brought to me alive by my
dredger on the 21st February in this year, and lived three weeks.
It was dredged in Weymouth Bay, near the mouth of the harbour.
The colour in this living specimen was very different from that of
the dead specimens I had previously obtained. When first brought to
me, the whole animal was a light greenish-drab, irregularly and thinly
sprinkled with pure white stars; the carapace and covering of the
abdomen were alike transparent, and the intestines could be easily

49 4

Miscellaneous.

seen beneath. I could also detect the breathing apparatus placed on
each side at the back of the mouth ; the movement was similar to
that of a long rope when gently waved at one end. After a few days’
confinement it changed colour : five or six broadish bands of a lovely
rose colour appeared, the bands of colour being restricted to the back
portion of each segment of the body; the tail also changed to the
same rosy hue, but in the course of two or three days the animal again
assumed its original colour. I have noticed this change of colour in
many of the Palcemonidce and Crangonidce , and I believe it to arise
from the transparency of the cuticle enabling any change in the body
itself to be seen through it, and that the change of colouring of the
body is occasioned by fear or some instinct. In all the specimens of
Nika I have obtained the shell is soft as in a new-moulted Prawn, and
in piercing them with a fine pin for preserving, the shell bends before
it. Is this of any value as a generic character ? M. Milne-Edwards
says they resemble Athanas "in possessing but a small rostrum
they also resemble them in their mode of locomotion, as they then
carry the external pedipalps and first pair of feet extended before
them in a line with their body; their movements are also slow and
deliberate, and they appear to progress by walking and not by
swimming; when alarmed they shoot backwards by striking forward
with their tail, as is the habit of all the long-tailed Crustaceans.

I now proceed to lay before you the information I have obtained
as to its habits.

I may assert that Nika is essentially a burrowing genus. I was
not prepared to find it so, as I considered its slender limbs and its
prominent eyes but ill-adapted for the purpose ; however, we live
and learn, and I have learned that practice is far better than theory;
had I relied on the latter I should have insisted that Nika edulis was
not a burrower.

In accordance with a plan which I have formed of attempting to
study the habits of any of our rarer marine animals I may have the
good fortune to meet with, I placed my prisoner in a vase with a
few weeds and some pebbles, that being the nature of the ground on
which it was dredged; 1 left it in this vessel for two days, and found
out it was not at home, and, in fact, that a pebbly bottom was not
its choice. I therefore removed it to a large earthenware pan in
which I had previously placed a few weeds, having filled it also to
the depth of three inches with coarse gravel; I then left it for an
hour, and on examining the vessel I could not find my friend; I
searched on the table, thinking it might have thrown itself out, but
it was without success; I turned over the stones and weeds, and with
the like result. I then commenced turning over the gravel, and at
last found that Nika edulis was a burrowing Crustacean. I accord¬
ingly transferred it for facility of observation to a vase, and placing
in it the same material, namely, the coarse gravel and weeds, in this
gravel it buried itself three several times. Burrowing in this loose
material was evidently a difficult matter ; it required great patience
and perseverance to overcome the difficulty occasioned by the loose
gravel constantly falling in on the excavator: it took the animal ten

Miscellaneous .

495

minutes to burrow to about tbe depth of three parts of its length.

I afterwards transferred it to a vase with sand to the depth of three
or four inches at the bottom; in this it quickly disappeared, three
minutes sufficing to completely cover itself. In this vase it was that
I made the following observations on it.

Its mode of mining is extraordinary: lying at the bottom of the
vase, it commenced proceedings by probing the sand around with its
third pair of feet, and inserting them to some depth in it; when it
found a spot suited for the purpose, that is, free from any large
stones, it at once commenced excavating. These operations were
carried out by the external pedipalps, which are very long and
strong, and also by the first, third and fourth pairs of legs ; the
second pair of legs, as may be supposed, are for this purpose per¬
fectly useless : they are as much as possible placed out of the way,
being bent up snugly with the hand turned backwards: the only
motion I could detect was a nervous action in the moveable finger,
constantly attempting to clutch objects, but not seizing anything.
The fifth pair of feet have a simple though useful office assigned
them: it is to support the body in the proper position until the
burrowing has progressed sufficiently to enable the burrower to do
without their support; they are then immediately called into more
active employment, and assist in the work of excavation. The spot
for burrowing having been selected, the little animal steadies its
body by means of its fifth pair of legs, and this allows the greatest
freedom of action to the body. The pedipalps perform a prominent
part in the burrowing; the nail on the last joint is curved slightly
forward, and the advantage of this is clearly seen, as in digging, the
pedipalps are forced into the sand or shingle, and are thus forced
forward and outwards, and they prevent the side of the burrow from
falling in ; the third and fourth pairs of feet are in constant motion,
probing the sand and loosening it, thus lightening the labour for the
pedipalps ; all these movements take place very regularly and at the
same time. A small hollow having been made, the animal raises its
body by means of its fifth pair of legs to nearly a right angle with
the bottom; its eyes, which are very large and carried at right angles
with the body, are thus suddenly thrown forward with a spring in a
line with the rostrum, and the hollow is surveyed; should it not be
of a sufficient depth the body is again lowered and the burrowing
continues, the eyes resuming their original position; when the hole
is sufficiently deepened, the eyes are again brought forward, the
antennae are thrown hack in a line with the body, and the animal
forces its head in the hole it has made ; this is facilitated by the
body being gradually raised by means of the fifth pair of legs ; the
head being inserted, the burrowing continues with increased energy,
and the animal assumes the position as in photograph No. 2 ; this
view shows the sand which has been thrown up accumulated in a
heap under the body.

I have occasionally found it continue in this position, but gene¬
rally it burrows perpendicularly, until only the tips of the antennae,
are visible. .......... ..

496

Miscellaneous .

I placed my captive in a glass vase, and his having selected the side
of the glass for burrowing (probably from the glass forming one firm
side to the work), enabled me to watch every movement; the sand
appeared to be passed to the mouth of the hole by the legs and false
legs, when it filled round the body and filled in as the animal passed
downwards. The antennae are delicately sensitive. I believe this
sensitiveness depends on the sense of touch: the slightest contact
with them sets the animal in motion (and this when it is buried
some depth), using every exertion to burrow deeper. It is evidently
a night-feeding genus, as it remained buried and inactive during the
day, but the state of the sand in the tank in the morning proved
that it had not been idle during the night.

From these facts I am justified in stating that Nika edulis is a
burrowing species (if not of a burrowing genus), and that its bur¬
rowing is only by day to hide itself from its enemies, and not to
procure food.

The description I have given of the colouring of this species will
be found to be different from that given by Risso, as stated by Mr.
Milne-Edwards. I should have great diffidence in differing from
these eminent naturalists had I not imagined that their descriptions
might have been taken from cabinet specimens. Had I waited to
describe my specimen until after its death, I must have described it
as it now is, namely, flesh-red ; I find all the thinner-shelled Crus¬
tacea change more or less of a flesh-red, with the exception of the
Crangonidce .— Proc. Zool . Soc., April 22, 1856.

NAUCRATES DUCTOR.

To the Editors of the Annals of Natural History .

Falmouth, November 1, 1856.

Gentlemen, —A shoal of the Naucrates ductor , Cuv., made its
appearance in shallow water. Custom House Pier, on Friday afternoon,
Oct. 31, 1856, and more than three dozen of them were caught in
nets, baskets, &c., by persons on the beach. I have procured species
of this interesting fish every year during my residence in this neigh¬
bourhood.

I am, Gentlemen, yours truly,

W. P. Cocks.

On Peculiar and Quasi-spontaneous Movements of the Plasmatic
Cells of certain Animals . By Prof. Kolliker.

I have just observed at Nice, upon a fine animal of the family of
the compound Ascidians, which according to M. Milne-Edwards has
not yet been described, a very peculiar fact, namely, movements of
the cells which occur in great number in the gelatinous substance
common to the whole bunch and formed of cellulose. These cells,
which are round or stellate and of very various forms, have, in the
living animal, a slow, but easily perceptible movement, consisting in
a constant change of form, so that the same cell, which was at one,
time round, becomes stellate or fusiform in different degrees, by the